Checklists were developed early in aviation as a safety mechanism. As aircraft became more complex, pilots committed more systems information and operating procedures to memory. Originally, checklists were used as memory joggers, but became a standard feature in most aircraft operations.
Checklist use is now considered very important to safe operations in commercial aviation as well as in many other industries, such as, those that involve the operation of complex machinery. As the content of checklists evolved, so did the way in which they were used. Pilots discovered that merely reading a checklist was often not enough to prevent mistakes in the operation of aircraft. Generally, procedures for using a checklist evolved, in that checks and backup mechanisms were built into these procedures. Typically, one pilot read the checklist while the other pilot performed the required action. The pilot reading the checklist confirmed that the second pilot had indeed performed the correct action. These procedures added levels of safety above and beyond the information content of the checklist alone and often saved an aircrew from performing the correct action on the wrong switch.
For example, in an emergency situation with an engine fire, the checklist may require the crew to shut down the engine that is on fire. This is usually accomplished by closing the fuel lever for the engine which stops the flow of fuel. If, during an already stressful situation, the pilot were to close the fuel lever for the wrong engine, the result may be catastrophic. In a situation such as this, the other pilot usually confirms that the pilot performing the checklist action has his/her hand on the correct fuel lever before closing it.
The ability of a multi-pilot crew to back each other up, especially in accomplishing checklist items, is an important safety factor. Federal Aviation Regulations eventually adopted a two-crew minimum requirement for all large commercial aircraft operations, whether the aircraft manufacturer required it or not.
Many small commercial aircraft and general aviation aircraft operate with only a single pilot. These aircraft do not have the advantage of a second pilot to facilitate reading of the checklist, carrying out the steps in the checklist or double checking the actions of the person carrying out the steps in the checklist.
Most aircraft rely on printed checklists. Recently, in light of the widespread incorporation of electronic flight displays, electronic versions of checklists have been developed. Most of these simply display the checklist on a multi-function display unit, however some will highlight the current checklist item on the display and allow the pilot to check off completion of the item. The primary goal of these electronic checklists is to mimic and supplement the paper checklist, not to reduce pilot workload.
Language differences are a drawback of paper and electronic checklists. Often, the aircraft will be operated by pilots whose native language is different than that used in the checklist. Although paper checklists are often easily translated and reproduced, the labels for the instruments and the writing on the instruments themselves may be very expensive to change. Often, the language on the instrument labels or the instruments themselves is not changed for monetary reasons, which can potentially cause confusion on the part of the pilots, especially during periods of high workload, e.g. takeoff and landing or emergencies. Therefore, performing the checklist in the native language of the pilots would produce a safety benefit.
Another drawback to paper checklists is they may be difficult to read during periods of reduced visibility in the cockpit, e.g., at night or if there is smoke in the cockpit. At times, checklist use may actually add to the pilot workload instead of reducing the workload. Often, pilots may be running multiple checklists at the same time and it may become confusing as to which checklist should take priority.
It would be desirable to have a system that provides or enhances the backup safety measures a second pilot provides, especially while accomplishing checklist items. The system would overcome the limitations of current-generation paper and electronic checklists while enhancing the safety of dual and single pilot operations.